This invention relates to valve assemblies, and more particularly relates to improved valve structures for fluid delivery systems employed in surgical procedures.
Laparoscopic surgical procedures have been improved by endoscopic direction of laser surgery resulting in reduced complication and risk of infection. For example, laser surgery on a gallbladder is accomplished by inflation of the cavity with a controlled flow rate of CO.sub.2 while the surgeon endoscopically directs the laser surgery on the target tissue. In addition, the target site is irrigated with pressurized irrigation solution followed by vacuum aspiration. The surgeon controls the irrigation and vacuum aspiration using a dual valve assembly referred to as a "trumpet valve" in which the valved irrigation and vacuum lines are independently controlled by digital manipulation within a commonly housed module held by the surgeon. However, the target tissue vaporized by the laser produces a smoke-like "laser plume" which can cloud the surgeon's vision through the endoscope, requiring that the clouding vapor be periodically removed by vacuum aspiration through the trumpet valve. The interrupting removal of the clouding vaporized tissue by the vacuum aspiration requires a difficult valve control which must regulate the vacuum flow rate at a level which will not adversely aspirate the CO.sub.2 pressure necessary to prevent deflation of the cavity. This valving control problem is eliminated by the improved valve structure according to the present invention.